function valida(){

var vEmail=document.contactForm.email.value;

var at="@";
var dot=".";
var Ist=document.contactForm.email.length;
var Iat=vEmail.indexOf(at);
var Idot=vEmail.indexOf(dot);

if(document.contactForm.name.value==""){
alert("Please enter name");
document.contactForm.name.focus();
return false;
}

if (isNaN(document.contactForm.tel.value))
{
alert("Telephone field should be a number")
return false;
}

if(document.contactForm.email.value==""){
alert("Please enter email address");
document.contactForm.email.focus();
return false;
}
	else if(vEmail.indexOf(at)==-1||vEmail.indexOf(at)==0||vEmail.indexOf(at)==Ist){
	alert("Please enter correct email");
	return false;
	}
	else if(vEmail.indexOf(dot)==-1||vEmail.indexOf(dot)==0||vEmail.indexOf(dot)==Ist){
	alert("Please enter correct email");
	return false;
	}
	else if(vEmail.indexOf(at,(Iat+1))!=-1){
	alert("Please enter correct email");
	return false;
	}
	else if(vEmail.substring(Iat-1,Iat)==dot||vEmail.substring(Iat+1,Iat+2)==dot){
	alert("Please enter correct email");
	return false;
	}
	else if(vEmail.indexOf(dot,(Iat+2))==-1){
	alert("Please enter correct email");
	return false;
	}
	else if(vEmail.indexOf(" ")!=-1){
	alert("Please enter correct email");
	return false;
	}

if(document.contactForm.msg.value==""){
alert("Please write your message");
document.contactForm.msg.focus();
return false;
}
}